You can calculate it on R with irr package.

Thanks Pedro - I haven't used R before but I've heard of it. Is there a lot of initial set-up required?

The installation is easy. And the main advantage is that the software is absolutely free and you have several packages (also free, with manuals with codes) to perform a lot of different analyses. If you are familiar to spss syntax, probably you won't have difficulty performing your analyses.

I agree with Pedro, r statistics is an amazing open-source software. Simply download R and the irr package, then you just call kappa2(ratings). Additionally, I would highly recommend downloading "r studio", it's an addon (GUI) for r which makes it much easier to use while also adding nice features such as markdown script.

Additionally you can also download the RCommander package, which is a GUI that allows you to perform several point and click data analyses. Besides that, it produces the code respective to the point and click action which will let you save some time in the future.

Kappa is not a difficult coefficient to calculate. You can do it easilly using excel. Try the file attached. With some effort, you can expand it to any number of classes.

It is just (observed - expected) / (Total - expected)

I believe that this exercise even will help you to understand the coefficient.

But start to use R anyway... :D

Thanks Pedro and Conal - your recommendations make a lot of sense for other analyses in the future.

Thanks Sandro for the file, also!

Here are a couple of trustworthy (IMO) online calculators.

http://graphpad.com/quickcalcs/kappa1.cfm

http://vassarstats.net/kappa.html

thanks Bruce - Graphpad looks really good for my purposes in terms of a "quick & easy" solution given I have more than two categories!